In recent years, energy efficiency has become an increasingly significant concern in many areas of commerce, including telecommunications. Energy efficiency has gained significance not only from an environmental point of view but also from an economical point of view. For example, for mobile network operators, reducing power consumption results in less money spent on operating expenses.
3GPP has worked on this topic, resulting in several ideas that can be studied, for example, in technical reports 3GPP TR 36.927 v. 13.0.0, entitled “Potential solutions for energy saving for E-UTRAN,” and TR 36.887 v. 12.0.0, entitled “Study on energy saving enhancement for E-UTRAN”.
Certain approaches to reducing energy consumption in mobile networks are built around overlapping cells where there is one or more so-called coverage cells which are always active and providing basic coverage and overlapping so-called boost cells that may be switched on or off based on network (NW) load generated by the user equipment (UE) in the cells. An example of this approach is illustrated in FIG. 1.
There are also solutions for non-overlapping cells, but these are dependent on having at least one coverage cell adjacent to the compensation cells that may be switched on or off based on said load. An example of this approach is illustrated in FIG. 2.
In the scenarios shown in FIGS. 1 and 2, on/off switching of cells is controlled by the NW without specific UE interaction. This happens either through a centralized operations-administration-maintenance (OAM) function based on e.g. load and traffic statistics obtained from the cells or via distributed/localized function based on information exchange among adjacent cells.
Although the above approaches may be adequate where UEs are moving from coverage cells into boost/compensation cells (in which case the coverage cell can switch on the latter), there is no good way for a switched-off cell with no adjacent coverage cell to detect when UEs are switched on and in need of service.